Introduction to the method of surface pretreatment of wood products

the surface treatment of wood products is done by coatingBecause wood contains resin, tannins, pigmentand and moisture, they have an effect on the adhesion, dryness and decorativeness of the coatingIn order to obtain a smooth finish, consistent pattern color and excellent performance of the cover coating, before the coating is coated, but also to the surface of wood products for pretreatmentThe main processes of pre-treatment are drying, deburring and so on1Drywoodhas porous, easy to absorb water and drainage, and has the characteristics of dry and damp, which causes the coating foaming, cracking and re-adhesive phenomenon, so the new wood needs to be dried to the water content of 8%12% before the coating is coveredThere are two methods of drying wood, natural drying and low temperature drying2Deburringwood products surface is degromed or polished, but there are always some not completely detached from the residual surface of the wood fiber, they once absorb moisture or solvent will wet the expansion and erect scraping hand, and affect the uniformity of surface coloring, so that the coated leave some uncolored small white spots, so the coating must be removed before coveringFor general wood products as long as a few sanding can be, advanced wood products can be used as follows:(1) on the surface brush thin insect gel varnish (worm glue: alcohol: 1:71:8), so that the burr can not only be erected, but also brittle, it is easy to use sand ingesting(2) wipe the surface with a moist clean cloth, so that the burr absorbs water to expand and erect, until the surface is dry with fine sandpaper or old sandpaper to polish itIf you add a little bone glue in the water, the effect is better(3) using the fire method, that is, brush with a thin layer of alcohol, immediately with fireAfter the blast of the fire becomes hard and brittle, easy to sand and clean, this method only applies to the treatment plane 3 Remove dirt contaminated with glue marks, oil stains and other dirt on the surface of wood products, you can first use sandpaper to polish it, and then use cotton yarn to scrub gasoline, if still not clean, you can use fine light short planing surface planing 4 Descant most conifer wood contains pine fat Pine resin contains pine-saving oil and rosin, which can affect the adhesion and color uniformity of the coating At higher temperatures, the pine fat spills out of the wood, causing the coating to stick The common method of cleaning pine resin is to clean with organic solvents, such as alcohol, turpentine, gasoline, toluene and acetone, etc., can also be used alkali cleaning, such as 5%6% sodium carbonate solution or 4% 5% soda solution cleaning, so that pine saponification, and then with a brush or sponge hot water scrub clean After the surface is clean, brush 12 insect paints at the cleaning site to prevent the pine fat in the wood inner layer from continuing to seep out 5 Bleaching many wood contains natural pigments, such as mulberry, eucalyptus and other yellow, purple, red pigment The pigment of wood is sometimes retained to play a decorative role, if the wood products to be painted into a light color or coated with the original material color independent of any color, wood products white blank surface to be bleached In general, bleaching is often carried out on local surfaces with darker colors, so that the color of the wood surface is consistent before the coating is covered there are many ways bleaching Commonly used bleaches are hydrogen peroxide (30% concentration) and ammonia (25% concentration) mixture (dioxywater: water: ammonia: ammonia: 1:1:0.2) or sodium hydroxide solution (dissolved 250 grams of sodium hydroxide in 500 grams of water) or hydrogen peroxide bleaching with a mixture of hydrogen peroxide and ammonia, if bleaching sheet, you can soak the single plate in the mixture, if the whole surface of bleaching, you can apply the solution to the surface of the wood, to meet the surface of bleaching requirements, and then wipe the surface with a clean wet cloth; bleached with sodium hydroxide solution, the liquid is applied to the surface of the wood and then coated with hydrogen peroxide after half an hour After treatment, scrub the surface of the wood with water, and use weak acid (e.g 1.2% acetic acid or oxalic acid) solution and sodium hydroxide, then scrub clean with water The above two methods have good effect on water willow, birch and so on, and the surface after bleaching does not change color for many years 6 Dyeing in order to get a beautiful texture, uniform color of the wood surface, wood products need to be dyed Wood dyeing can generally be divided into water color dyeing and wine color dyeing two kinds The water color is the aqueous solution of the dye, and the wine color is the alcohol solution of the dye The preparation of water color is best with acidic dyes, commercially available yellow powder and hena powder is made from a mixture of several acidic dyes When dyeing with water color, the moisture is slower, the dyeing is uniform, and the price is low, and the use is convenient Its main disadvantage is that water makes wood hair, to be sanded to eliminate the hair phenomenon the preparation of wine color is best with alcohol-soluble salt-based dyes The wine color is the use of alcohol as a solvent, it is volatile, do not wet wood, eliminate the phenomenon of wood surface hair, and dyed bright colors The disadvantage of wine color dyeing is that it is prone to the phenomenon of uneven tone If the use of wine color dyeing, can be called alcohol solution dye 6 points, alcohol 70 points and insect gel varnish 24 points, after mixing evenly, with manual brush or spray dyeing dissolve dyes, whether water color dyeing or wine color dyeing, it is best to operate in a glass, ceramic jar or enamel basin, do not use metal containers, so as not to cause discoloration